Further comparing the Turbo Concepts Stage 1 turbochargers to the Borg Warner K04’s, the chart below is an illustration of how the exhaust gas temperatures compare.
The pre-turbo temperature is recorded via the car’s Exhaust Gas Temperature sensors which are RS6 units.
Audi RS6 EGT Sensors for B5 S4
Post turbo temperatures are recorded via a temperature probe located at a pre-catalytic converter bung that is also used with a wideband O2 sensor.
Auber Instruments K-type thermocouple
Temperature readings at about the same manifold boost pressure are shown below.
Turbo Concepts and BW K04 Exhaust Gas Temperatures compared
With the EGT’s starting slightly higher on the Turbo Concepts turbo’s the higher readings throughout are expected.
Nothing notable jumps out at me from these results, both turbo’s look to perform about the same under the conditions that these readings were made.
When I received the Turbo Concepts Stage 1 turbochargers I had inquired about what boost level to operate them at. I was advised to aim for an initial ramp up to 18-20 psi then start tapering the boost off, try to reach 15 psi by 5000 rpm and down to 12 psi by redline. About what the blue lines on the chart below look like.
Turbo Concepts Stage 1 mild boost
Initially after installing the TC turbo’s my intent was to record some basic performance data that I could compare with the other turbochargers that I have recorded. That meant I had to operate the Turbo Concepts turbochargers at a boost level higher than was recommended.
With the initial data collection behind me I’ve taken the opportunity to drop the boost and see what happens. The chart above is the result of the first revision to the tune. The red boost lines are the Turbo Concepts turbochargers, the blue boost lines are the product of BorgWarner K03’s and the NVR Stage2+ tune.
Just by chance the NVR tune with the K03’s is a close boost profile to that recommended for the Turbo Concpets turbo’s – this provides an interesting case to look at for similarities and differences.
There are a couple of notable differences in the K03’s vs TC Stg1 results, first is that the TC turbo’s are being operated at a slightly higher boost level. This was the first revision to the tune and I was taking a stab at the values for LDRXN that I thought would produce a boost curve close to what Turbo Concepts had recommended. The second notable point is that the log with the K03’s was made during the summer time, with air temperatures of 70 degF. The Turbo Concepts data was recorded in December with air temperatures of 20 degF. The large gap between the Intake Air Temperatures is evidence of these different conditions. The K03’s are the dashed lines and TC turbo’s the solid lines.
Given these two considerations, higher boost and colder air, one would expect higher mass airflow readings from the Turbo Concepts turbo’s, which is the case. I would expect that if the conditions were more alike, similar boost and similar air temperature, the mass airflow would also be more similar. This leads to an interesting conclusion, it’s likely that the engine would perform about the same with the TC Stg1 turbo’s as it would with the BW K03’s when operated at this boost profile. I’ve found mass airflow to be a good predictor of wheel horsepower.
This leads to a question, how can the Turbo Concepts Stage 1 turbo’s reach the advertised 380 whp if they are being operated at the recommended boost level? According to the results I’ve obtained the TC Stg1 should be making about 300-310 whp at the recommended boost level.
To get close to 380 whp the boost will need to be raised. When I’ve operated the TC Stg1 at around 22 psi I am seeing close to 380 g/s towards the top end which should put the car close to 380 whp.
Turbo Concepts Stg1 24 psi taper to 22 psi
This leaves an unresolved issue, how to reach the advertised wheel horsepower at the boost level Turbo Concepts recommends operating these turbochargers at.
In the last post about the Turbo Concepts turbochargers I mentioned that the temperature rise across the compressor was looking a bit better than what I recorded with some other turbochargers. To try to simplify the process of making a comparison I’ve chosen to assess the products in the following way.
I chose 5500 rpm as the engine speed at which to compare the temperature rise. As the chart below illustrates, the rise in temperature is reasonably linear past 4000 rpm, yes there is some slight curvature to the data, but for my purposes this assumption of linearity with engine speed isn’t something that I feel will change the outcome of the comparison. If I took the reading at 6000 or 6500 rpm the relative differences between products would still be like that made at 5500 rpm.
It is clear that the temperature delta at the start will exist throughout, though the magnitude does decrease some in the example below. I have chosen some datasets, from many, that have starting deltas in the same ballpark, around 20-30 degF, and by using at least four samples and then averaging them I hope to show a ‘typical’ case comparison.
Below is how the BW K04’s, FT F21’s, TTE 550’s and TC Stg1 turbochargers compare. Again, this is the rise in the temperature through the turbochargers compressor when the turbo’s boost profile is approximately the same and with approximately similar starting delta’s. The conditions are not exactly the same in each case, which is why there are 4 to 5 samples taken and then averaged for each turbocharger, to give a general idea of how the products compare in this regard.
K04’s and Hybrids Compared
It’s clear that three of the products perform about the same as one another, and one, the Turbo Concepts, performs differently. The Turbo Concepts turbocharger produces a lower temperature output from the compressor versus the other turbochargers.
This lower temperature produced by the TC turbo’s is a good thing, but as I discussed in the earlier post, the intercooler and water-methanol injection come into play before the charge air reaches the engine, resulting in an intake air temperature that is not much different between these products.
